Dielectric porcelains whose primary component is CaZrO3 have traditionally been used for high-frequency dielectric resonators, filters, laminated ceramic capacitors, etc. Desirably these laminated ceramic capacitors, etc., offer lower temperature coefficient of dielectric constant in order to support recent devices operating at higher frequencies (approx. 100 MHz to 2 GHz). For the internal electrodes of laminated ceramic capacitors, base metals of low specific resistance must be selected in order to ensure low ESR (equivalent series resistance), small loss in the high-frequency range (high Q-value), and low cost, and for this reason Cu is used instead of Ni or Pd. Requirements for the dielectrics include high Q-value, low temperature coefficient of dielectric constant, and high reliability, and, in relation to the use of Cu in internal electrodes, possibility to be sintered at low temperatures of 1080° C. or below, and being a non-reducing material in order to prevent oxidization of Cu. Also for environmental reasons, dielectrics free of Pb and Bi are desired. Dielectric porcelain compositions meeting these requirements are already known, and applications of these dielectric porcelain compositions for laminated ceramic capacitors are described in multiple patent literatures.
For example, Patent Literature 1 describes a non-reducing dielectric porcelain composition that contains (Ca1-xSrx)m(Zr1-yTiy)O3-zMnO2-w SiO2 as its primary component and a(LiO1/2—RO)—(1−a)(BO3/2—SiO2) as an additive (where RO represents at least one of SrO, BaO and CaO), where this non-reducing dielectric porcelain composition “can provide a dielectric porcelain which can be sintered at low temperatures of approx. 1000° C. or below, thereby permitting use of copper as the electrode material, which also offers high Q-value and dielectric constant and stable temperature characteristics of dielectric constant” (Paragraph [0005]). However, how this composition can improve the longevity traits of laminated ceramic capacitors using Cu in internal electrodes has not been studied sufficiently.
Also, Patent Literature 2 describes a dielectric porcelain composition that contains a complex oxide expressed by (CaO)x(Zr1-yTiy)O2, Mn compound, and glass component expressed by (aLi2O-bB2O3-cCaO), characterized in that “this dielectric porcelain composition can be sintered in a reducing ambience of 1000° C. or below, offers high dielectric constant and stable temperature characteristics of dielectric constant, and achieves significant improvement of Q-value, particularly in the high-frequency range (GHz band), by achieving Qf=10000 or more in the high-frequency range” (Paragraph [0015]). However, how this composition can improve the longevity traits of laminated ceramic capacitors using Cu in internal electrodes is not studied sufficiently.
On the other hand, Patent Literature 3 refers to the longevity traits of laminated ceramic capacitors, as well, describing a dielectric porcelain composition comprising: a primary component that contains a dielectric oxide expressed by the composition formula {(Ca1-xMex)O}m(Zr1-yTiy)O2, where the symbol Me indicating an element name in this composition formula is at least one of Sr, Mg and Ba and the symbols m, x and y indicating composition mol ratios in the composition formula meet the relationships of 0.8≦m≦1.3, 0≦x≦1.00 and 0≦y≦1.00, respectively; a first auxiliary component that contains a V oxide; a second auxiliary component that contains an Al oxide; a third auxiliary component that contains a Mn oxide; and a fourth auxiliary component whose primary component is SiO2 and which also contains at least one type of oxide selected from the group that includes MO (where M is at least one type of element selected from the group that includes Ba, Ca, Sr and Mg), Li2O and B2O3, where the ratio of each auxiliary component relative to 100 mol of the primary component is 0 mol<first auxiliary component<7 mol for the first auxiliary component (equivalent values of the V oxide being V2O5), 0 mol<second auxiliary component<15 mol for the second auxiliary component (equivalent values of the Al oxide being Al2O3), 0 mol<third auxiliary component<5 mol for the third auxiliary component (equivalent values of the Mn element in the Mn oxide), and 0 mol<fourth auxiliary component<20 mol for the fourth auxiliary component (equivalent values of the oxide); wherein a method of manufacturing such dielectric porcelain composition comprises: a step to prepare a pre-reaction material by mixing some of the auxiliary component materials excluding at least the third auxiliary component material or fourth auxiliary component material or both, with a starting material prepared to obtain a primary component material; a step to cause the prepared pre-reaction material to react to obtain a reacted material; and a step to mix into the obtained reacted material the auxiliary component material(s) excluded when the pre-reaction material was prepared to obtain a dielectric porcelain composition material, where such manufacturing method is characterized as being able to “manufacture a reduction-resistant dielectric porcelain composition offering excellent low-frequency dielectric characteristics and greater longevity under stress in terms of insulation resistance” (Paragraph [0013]). However, particularly desired sintering temperatures described as 1200 to 1300° C. or low-temperature sintering to permit use of Cu in internal electrodes is not sufficiently studied.
Patent Literature 4 describes a laminated ceramic capacitor whose primary component is a CaZrO3 compound and which also has a ceramic body containing Mn or other additive, characterized in that such laminated ceramic capacitor can offer improved longevity traits when segregation deposit of Mn—Cu—O is suppressed in a cross-section of the ceramic body.
In light of the aforementioned situation, the inventors of the present invention studied ways to improve the longevity traits of laminated ceramic capacitors using Cu in internal electrodes and found that the Ca/Zr ratio and Mn, Li, B and Si contents of the CaZrO3 dielectric porcelain in such laminated ceramic capacitor would determine the longevity of the laminated ceramic capacitor and also found conditions for Ca/Zr ratio and Li—B—Si composition ratio that would give a denser CaZrO3 dielectric porcelain at the Cu melting point of 1080° C. or below, even when the contents of Li and B are suppressed so as not to cause the longevity to drop, to permit use of Cu in internal electrodes (Patent Literature 5).